Water Color Odor Appearance and Taste
Your First Evidence of a Problem
Secondary Water Quality Issues
Is your water safe to drink? Does it smell funny or is it cloudy or off-color?
The increase in the reported cases of chemical spills, leaking oil tanks,
toxic waste sites, and pesticide use may make you wonder about the quality and
safety of your water. what is in your water. Whether you get your water from a
public or a privately-owned public water system, or your own well or spring,
having a safe source of drinking water is vital to the health of you and your
Changes in the appearance, taste, odor, and color may be your first evidence of
a problem. Color in water can be caused by a number of contaminants such as iron
which changes in the presence of oxygen to yellow or red sediment. Color from
iron is referred to as "apparent color" rather than "true color". True color is
distinguished from apparent color by filtering the sample.
The most common source of true color is decaying organic matter such as
the yellowish "tea color" of water in tundra or wet bogs. True color is mostly
found in surface water, although ground water may contain some color if the
aquifer flows through a layer of buried vegetation, such as from a long buried
slough of a river.
Color is not a toxic characteristic, but is listed by the
as a secondary (aesthetic) parameter affecting the appearance and
palatability of the water. When chlorinated, color-causing organic matter may
form chlorinated organic compounds such as
trihalomethanes. Chloroform is a common trihalomethane, and is along with
several others, considered to be a potential carcinogen. For this reason ADEC
limits total trihalomethanes (TTHM's) in public water supplies to 0.1 ppm (100
ppb). Color is measured in units based on a platinum-cobalt standard solution
which forms a yellow tint and is limited to 15 units in public water supplies.
Color can be removed by activated carbon filters, sometimes marketed as
taste and odor filters. The activated carbon or charcoal must be replaced after
a period of time when its capacity for adsorption of the color is exhausted.
Another treatment method is coagulation and sedimentation using alum or other
chemicals. This process is normally used only in large plants since its
complexity requires the care of a trained water treatment plant operator.
Color analysis is done by visual comparison to a set of platinum-cobalt
standards in Nessler tubes. Sample collection is done in a clean rinsed bottle
which should be refrigerated if stored for more than a few hours.
If the color of the water exceeds 15 color units and the water is being
chlorinated, we suggest having the water examined for total trihalomethanes by
gas chromatography. This is a more expensive and time consuming analysis, but is
extremely sensitive with detection limits down to the ppb level. Sample vials
specially designed to eliminate the air space above the sample are required for
sampling. For laboratory testing for organics and other chemicals, please
Drinking Water Testing Website.